Preheat oven to 350 degrees F and grease a 9" x 9" baking pan.
In a mixing bowl, whisk together dry ingredients: flour, cocoa powder, and salt.
In a separate mixing bowl, combine wet ingredients: brown sugar, granulated sugar, vanilla extra, oil, and eggs.
Gradually stir in the dry ingredients to the wet until fully incorporated, but do not over-mix.
Fold in about 3/4 cups each of chopped peanut butter cups and chocolate covered pretzels.
Pour the batter into the prepared baking pan. Evenly sprinkle the remaining peanut butter cups and pretzels across the top of the batter.
Bake for about 20 to 23 minutes. Let cool in the pan about 30 minutes or so and cut into squares.
Dust brownies with additional cocoa power and a bit of flaky sea salt, and enjoy!